I use Yesterdays News. I usually find it at either Petsmart or Petco, around here the Petco is the only one that has the softer texture and unscented type I like to use for my rats. You can find it in either a cat litter type or a small animal type. I buy the cat litter type because it's much cheaper.
I use Carefresh, but that's mainly because I was given bags of it for free :roll: I don't like it much, personally, because I can't scoop anything out, I have to dump all of it at once. I've never used YN, but from what I've seen/heard it seems like a good choice.